Molybdenum diaryl-dithiocarbamate complexes and their application as single source precursors to MoS2

Molybdenum diaryl-dithiocarbamate (DTC) complexes have been prepared and their suitability as single source precursors (SSPs) to nanoscale MoS2 investigated. Heating thiuram disulfides, (Ar2NCS2)2, with [Mo(CO)6] in acetone affords diamagnetic Mo(IV) complexes [Mo(S2CNAr2)4] proposed to adopt a dodecahedral structure. While relatively stable in the solid-state, slow oxidation in solution affords Mo(V) cations, with [Mo{S2CN(p-tolyl)2}4]2[Mo6O19] being crystallographically characterized. Mo(VI) dioxo complexes cis-[MoO2(S2CNAr2)2] have also been prepared and the molecular structure of cis-[MoO2(S2CNPh2)2] crystallographically determined. In solution, oxo-loss with concomitant metal reduction affords Mo(V) dimers, being established crystallographically for [MoO{S2CN(p-tolyl)2}2]2O. To assess their thermal stability, extensive thermal gravimetric analysis (TGA) studies have been carried out in the solid-state and in a range of high boiling point solvents. These show that decomposition onset and (likely) decomposition profiles are strongly solvent dependent. Thermolysis of [Mo{S2CN(p-tolyl)2}4] has also been compared to that of [Mo(S2CNEt2)4], allowing different decomposition pathways to be elucidated. Heating both [Mo{S2CN(p-tolyl)2}4] and cis-[MoO2{S2CN(p-tolyl)2}2] under argon at 450 °C results in formation of powder and nanoparticles of MoS2 respectively, while in air α-MoO3 is exclusively formed. Decomposition of [Mo{S2CN(p-tolyl)2}4] in oleylamine, at 230 °C affords nanosheets of MoS2.